Books you must have:
Tecnicas Participativas Para La Educacion Popular The best resource book for popular educators, combines technique (lots of activities) with method and embodies the work of popular educators in Central America.
Educating for a Change. My second favorite. Great book for both its tools and its thoughtful discussion of many challenges facing popular educators -- see the useful material for facilitators, for example.
Education for Changing Unions. Great book, takes the ideas and skills of the people who brought us Educating for a Change, and shows their use in the Canadian union context.
Games for Actors and Non-actors (free online edition). By the Brazilian popular educator and dramatist Augusto Boal. Rich collection of activities and ideas for "theater" and education.
Other important books:
The Ignorant Schoolmaster. by Jacques Ranciere. Shares and analyses the work of Joseph Jacotot, an early 19th century French educator. This book challenged many of my basic assumptions and goals and now informs the way I think about popular education.
Training for Transformation, A Handbook for Community Workers. Reflects the practice of educators in Southern Africa. Lots of good material, pretty didactic -- less open-ended than Educating for a Change, say. See the review and order info on the Popular Education News site.
The Workplace Project/Centro Pro Derechos Legales. http://www.workplaceprojectny.org/index.htm